Field of the Disclosure
The present disclosure generally relates to a dirty fluid pressure regulator and control valve.
Description of the Related Art
Downhole tools are frequently used in the drilling of a crude oil and/or natural gas well. Such tools may be operated by drilling fluid pumped down a drill string. The operation of such tools may require an onboard pressure regulator to smooth pressure fluctuations and step down pressure in the drill string and/or an onboard control valve to selectively operate various functions of a downhole tool of a tool string, such as a bottomhole assembly. The drilling fluid may include a base liquid, such as refined or synthetic oil, water, brine, or a water/oil emulsion. The drilling fluid may further include solids suspended in the base liquid, such as organophilic clay, lignite, and/or asphalt, thereby forming a mud.
Prior art pressure regulators include supply, vent, and function ports allowing for incoming and outgoing pressurized fluid flow to operate a fluid-driven tool. The supply and vent ports are selectively opened and closed by seal rings attached to a seal carrier that is located within the chamber of the regulator. The seal rings move with the seal carrier for selective alignment with the ports. The seal carrier is moved by a spring-driven piston. The supply and vent ports are formed through seal plates and the seal rings are biased into engagement with the seal plates by energization springs.
As the fluid-driven tool consumes the pressurized fluid, the spring-driven piston moves the seal carrier to clear the supply seal ring from the supply port and to align the vent seal ring with the vent port, thereby allowing the fluid to enter the regulator from the supply port. Conversely, when the internal pressure of the regulator is greater than the set point, the spring-driven piston moves the seal carrier to align the supply seal ring with the supply port and clear the vent seal ring from the vent port, thereby protecting the fluid-driven tool from overpressure.
Reliance on the spring-driven piston to move the seal carrier requires that a regulator include a large chamber. A large chamber causes the prior art regulators to be bulkier and less streamlined making them unsuitable for fitting within walls of or annuli between oilfield tubulars. Further, the seal rings and seal plates of the prior art regulators are made from metal which is subject to abrasion by particulates of the drilling mud lodging between the seal plates and the seal rings.
Further, the traditional seal plates and rings result in significant friction resisting movement of the seal carrier. This friction constrains the ability to regulate high pressure with the desired low “dead band”. Dead band is an industry term that describes the change in outlet pressure required to generate a dynamic response from the regulator. The traditional subsea regulator design results in high dead band which produces highly variable working pressures.
It is thus desirable to provide a regulator that reliably and accurately regulates pressure at or near the set point with low dead band while being resistant to solids and which can be scaled down to small sizes suitable for downhole use.